Removal of phosphate from aqueous solution by ferrihydrite/bagasse composite prepared through in situ precipitation method

Ferrihydrite/bagasse composite adsorbent (FH/SCB) was prepared by in situ precipitation method to remove phosphate from aqueous solution. Effects of precipitation pH on adsorption performances of the composites were investigated and adsorption performances and mechanism of phosphate on the composite prepared at the optimum pH for phosphate were studied. Results showed that precipitation pH played a key role on the morphology and adsorption performances of the FH/SCB. SEM-EDX, TEM, XRD and Zeta potential illustrated that ferrihydrite was loaded uniformly on the bagasse surface at pH 4.5, and the obtained composite (FH/SCB4.5) with higher isoelectric point exhibited the maximum adsorption capacity for phosphate. pH and adsorption isotherm results depicted that FH/SCB4.5 showed higher adsorption capacity at lower solution pH. Obvious synergistic effects were observed in co-ions experiment, and both the common anions (NO3-,Cl-, SO42-) and cations (K+, Ca2+, Na+, Mg2+) could promote the phosphate adsorption. Adsorption mechanism analysis showed that electrostatic attraction and inner-sphere complexation involved in the phosphate adsorption. Furthermore, wastewater treatment results showed that more than 99.7 % of phosphate could be removed from wastewater by FH/SCB4.5, demonstrating that the as prepared sorbent had great potential in practical application.